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ОПРЕДЕЛЕНИЕУДЕЛЬНОГО ЭЛЕКТРИЧЕСКОГО СОПРОТИВЛЕНИЯ ОРЕХОВОГО
ДРЕВЕСНОГО УГЛЯ
Токторбаева Г.П.
Преподаватель Ошский государственный университет, Кафедра "Естественно-научные дисциплины ",
Ташполотов Ы. д.ф.-м.н., профессор Ошский государственный университет, Кафедра "Экспериментальная и теоретическая физика "
Садырова М.М. Доцент
Ошский государственный университет, Кафедра "естественнонаучные дисциплины"
DETERMINATION OF SPECIFIC ELECTRICAL RESISTANCE OF WALNUT CHARCOAL
Toktorbaeva G.
Teacher Osh State University Department of Natural Science Disciplines
Tashpolotov Y.
Doctor of Physics and Mathematics, Professor Department of Experimental and Theoretical Physics
Sadyrova М.
Docent Osh State University Department of Natural Science Disciplines DOI: 10.5281/zenodo.6696562
Аннотация
В статье изложены результаты экспериментальных определений электрических и удельных сопротивлений угольного порошка и брикета орехового древесного угля и данные сравнений с электропроводностью монокристалла графита. Угольный порошок и брикет имеет более низкое удельное электрическое сопротивление (8 Ом*мм2/м и 7 Ом*мм2/м) по сравнению с электросопротивлением монокристалла графита оси С. Это связано с тем, что угольные брикеты и таблетки из порошков древесного угля получены методом выдавливания и прессования в пресс-форме. Установлено, что удельное сопротивление порошка и брикета и вольт-амперная характеристики различны. Показано, что с повышением температуры композита, удельное сопротивление также возрастает.
Abstract
The article presents the results of experimental determinations of the electrical and resistivity of coal powder and a briquette of walnut charcoal and data of comparisons with the electrical conductivity of a graphite single crystal. Coal powder and briquettes have a lower electrical resistivity (8 Q^ mm2/m and 7 Q^ mm2/m) as compared to the electric resistance of C axis graphite single crystal. This is due to the fact that coal briquettes and tablets from charcoal powders are obtained by extrusion and pressing in the mold. It has been established that the resistivity of the powder and the briquette and the current-voltage characteristics are different. It is shown that with an increase in the temperature of the composite, the resistivity also increases.
Ключевые слова: древесный уголь, удельное электросопротивление, сила тока, графит, угольный порошок, угольный брикет, выдавливание, прессование, вольт-амперная характеристика.
Keywords: charcoal, electrical resistivity, current strength, graphite, coal powder, coal briquette, extrusion, pressing, current-voltage characteristic.
Introduction
Charcoal is similar in composition to coal, in which carbon is also the main element. In fact, both charcoal and coal are based on wood. Only in coal, wood decomposed for many centuries with limited access to oxygen, and charcoal is charred wood, which was partially burned with a lack of oxygen. In the process of charring, most of the moisture, sulfur, phosphorus and oxygen leave the composition of charcoal. In this case, the losses of carbon and hydrogen are minimal. The ash also remains, which is not removed during charring. The charcoal itself is easily ignited and gives a lot of heat.
Modern enterprises that produce charcoal are equipped with special retort furnaces. The whole process takes place directly in such a furnace. The pyroly-sis chamber and coal drying chamber are separated, thanks to which the heat is used to great advantage. Moreover, the flame is formed due to the combustion of volatile products, and not due to the combustion of firewood. Volatile products that are released during combustion are transferred back to the furnace and burned there.
It is known from the literature [1-3] that the pyrol-ysis process consists of three main stages: the first stage, at temperatures up to 260°C, moisture is released from the raw material; the second stage, at a temperature of 280-387°C, liquid (dark brown liquid resin) and gaseous substances are released [2. p.135-140]; the third stage, the temperature at this stage starts from 400°C to 465°C and the pyrolysis ends, charcoal remains in the retort.
In [4], without access to air in the temperature range from 950 to 1000 the following was experimentally obtained from coal of the Uzgen basin: 95% coke, 0.2% tar, 1.8% pyrogenetic water and 3% gas. To purify impurities, grinding of coal was carried out successively in a shock and ball mill. A sieve analysis was made through a brass sieve with a mesh size of 0.125 mm and weighing 1000 g of powder and adding 60% sulfuric acid solution and heating for 30 minutes. Even purified analyzed samples are washed in running water, filtered through a cotton cloth. The purified residue of coal powder was dried in an oven at a temperature of 130°C.
Academic V.V. Korshanov synthesized a linear polymer of carbon during the catalytic oxidation of acetylene-C2H2 and called carbon, containing up to 99% carbon, and it turns into graphite only at temperatures above 2000 ° C, without air access. The studies were carried out at temperatures from 2750°C to 3000°C in fire furnaces using acetylene with oxygen, without air access [5, p.26-28].
In [6], the influence of the process temperature on the properties of biochar was investigated and was distinguished, and further temperature increase improves the pore stability and conductivity of the material. This phenomenon was probably associated with both the formation of new C-C bonds and rearranged graphite and quasi-graphite domains formed during pyrolysis, as shown by Raman scattering. The most significant result of this study was that even though pure biochar prepared at 1000°C showed lower conductivity with respect to CS when it was used in a highly dispersed state in the composite, the electrical properties of the bio-char-containing composite were several orders of magnitude higher. , than composites containing CS, both materials were brittle than pure resin, with 10000C showed higher performance. Mechanical properties also showed a direct correlation with dispersion.
As is known [7, p. 74-81], current-voltage characteristics (CVCs) of nano and microsystems are perhaps the most accessible for experimental studies and, at the same time, very informative for determining the features of generation, recombination and transport of charge carriers in these systems and construction of theoretical models of ongoing processes of nanostructural systems. Nano micropowders of carbon with various dispersions, obtained on the basis of hydropercussion formulated by us pressed into cylindrical tablets with a diameter of 6 mm and a height of 8 mm. The sample, prepared in a thin way, was placed in an oven preheated to 800-900°C and kept for 1-3 hours. After heat treatment at the appropriate temperature in an oven, the tablet was slowly cooled to room temperature.
The experimental part
We have explored the process of pyrolysis of walnut shells in the temperature range of 100-550°C with the formation of charcoal without air access. The inorganic component in the shell is about 25%, while the organic part is 75%. It has been established that the yield of charcoal from walnut shells at 550°C is 33.3% by weight, the percentage of carbon is about 84% and the ash content is 0.1%For the experiment, 500 g of the test sample was taken, which was ground in a ball mill and passed through a sieve with a mesh size of 0.04 mm. Next, the test sample with a certain dispersion was placed in a beaker with a capacity of 500 cm3, in which 300 ml of a 40% sulfuric acid solution was added and heated for 20 min.
The resulting coal suspension was stirred with an electric stirrer for 5 min, after which the samples were washed with distilled water. Coal powder was dried at a temperature of 130°C. For re-analysis, 100 g of coal powder was taken, which was burnt in a muffle furnace at a temperature of 500°C. The mineral composition of charcoal ash was determined by the spectrophotometric method. The data obtained are presented in table 1.
Table1
Mineral composition of coal ash
№ Element The concentration of chem. element in %
1 Si Traces
2 K -
3 Ca -
4 Mg -
5 Fe -
6 Mn -
7 Zn -
8 Cu -
9 Se -
10 I -
11 Ba -
12 As -
13 P -
14 Ni -
15 Na -
For research current-voltage characteristic of charcoal powder and briquette, schematic representation, which is shown in fig. la
pue. 1a
H
\
J 11 1 : V' ft
Tjrii J \mu □
-
Figure 1a:
1- mechanical clamp
2- plastic insulator
3- coal powder
4- electric wire
5- multimeter
Figure 1b:
1- mechanical clamp
2- plastic insulator
3- coal briquette
4- electric wire
5- multimeter
Coal powder(poured into plastic container) and briquette reinforce with mechanical clamp and connected with electric wires to a standard multimeter and measured the volt-ampere values of the sample. Using Ohm's law for a circuit(R=U/I) and formulap=R*S/Ide-termined the electric and specific resistances of coal
powder and briquettes and compared with the electrical conductivity of a single crystal of graphite. Graphite single crystals are characterized by a very high degree of electrical resistivity (Table 2). The table shows the electrical resistivity values of single crystals of graphite and pyrolytic graphite at 20°C [7, p.36-38].
Table2
Num. Name of substance Pa, Q • mmJ/m Pc , Q • mm2/m Pc/Pa
1 Graphite 0,99-1 10000 104
2 Charcoal briquette 0,6 5000 0,8*104
3 Charcoal powder 0,5 4000 0,7*104
Charcoal briquette and walnut husk powder have a relatively low electrical resistivity (8 Q • mm2/m h 7 Q • mm2/m) compared with the electrical resistance of a graphite single crystal along the axisC(pc). This indicates that in coal briquettes and powders obtained by extrusion and pressing in a mold, electric charges are transferred along theA(pa)axis of coal crystallites.
It has been experimentally established that the specific resistance of coal powder and briquette has a different value.
We have also studied the temperature dependence of the electrical resistance of graphite(2) and non-graphitized(l) burnt Greek coal. The results obtained are shown in Fig. 1.
100 200 300 400 500 600
t0C
Fig. 1. The dependence of the electrical resistance of carbon materials on temperature
It can be seen from the dependences obtained that the temperature dependences of the electrical resistance of graphite (2) and non-graphitized (1) burnt charcoal differ significantly from each other.
Based on the data obtained, the following conclusions were made:
1. Charcoal briquette and walnut husk powder have a relatively low electrical resistivity (8Q • mm2/m and 7Q^ mm2/m) compared to the electrical resistance of graphite single crystal.
2. It has been established that for a burnt coal briquette, the temperature dependence of the electrical resistance has the values of the minimum specific electrical resistance depending on the heat treatment temperature in the range of 100-200 °C. This is apparently due to the fact that the higher the exposure temperature, the more intensely the atoms in the charcoal briquette vibrate and, as a result, the resistivity increases, and at a lower temperature, a minimum of resistivity is observed.
References
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